The box itself has been outside the station for several years, one of the last "police boxes" still working in the UK.

The Google Maps TARDIS tour allows web browsers to click on the map to "enter" the box, and instead of the usual police box interior, they are presented with a 3D representation of a TARDIS "console room".

The TARDIS as it appears in Doctor Who is referred to as a Type 40. Its "chameleon circuit" is intended to allow it to blend into any surrounding.

One of the series leitmotifs is that the chameleon circuit of the Doctor's TARDIS does not work, and it is stuck in the police box design it adopted when the Doctor first came to London in the 1960s.

Google has engineered the feature to mark the 50th anniversary of the Doctor Who TV series.

When police boxes were first launched in the late 19th century they were intended to serve as mobile police stations. They were later equipped with telephones linked to nearby police stations.

The iconic blue police box adopted by the TV series Doctor Who for the exterior of its broken time machine, the TARDIS, was designed in 1929 by Gilbert MacKenzie Trench.

The box's top-light was intended to alert beat police to call into their base station. And its telephone was designed for passers by to summon police assistance.

At their peak in the 1950s, there were almost 700 on the streets of London. Now, only a handful remain, and few are actually working police mobile units. The Earl's Court police box is a rare exception.

The BBC's use of the police box was the subject of a brief skirmish between the broadcaster and London's Metropolitan Police in the '90s when the BBC applied to trademark its use.

The police objected, but the Patent Office ruled in the BBC's favour as there was no record that the police had ever registered it as a trademark in the first place. Since then relations between the cops and the Time Lords could be described as "cordial".

Details of the TARDIS interior and its features - including its "console room", the disaster-warning "cloister bell" and its telepathic circuits - have for a long time been a part of the show's canon.

Though the Doctor's TARDIS was the one seen mostly on screen, several other TARDISes have appeared in the series, notably those of rival Time Lords such as The Rani, The Meddling Monk and The Master.

For the keen-eyed, the Doctor's TARDIS featured a St. John Ambulance badge on its main door from 1963 to 1966, a detail which was reinstated by the producers of the new series when Matt Smith took on the mantle of the 11th Doctor in 2010.